1. Field of the Invention
This invention relates to a method for checking the contacts of an enclosed type switching device including an air-blast circuit breaker, gas circuit breaker or the like, and an auxiliary apparatus for use with the switching device for application of the method.
2. Description of the Prior Art
In conventional methods, the electric contacts of the switching device are visually observed in order to check a degree of damage or deterioration thereof. In the case of an enclosed-type switching device such as an air-blast circuit breaker or gas circuit breaker, it is necessary to take off the partition walls or casings enclosing the contacts for visual inspection of the contacts and after completing the inspection, to assemble them again.
Especially in recent years, the increased voltage and capacity of the electric power transmission system has remarkably increased the short-circuit current at ground-faults or the like, thereby subjecting the contacts of the circuit breakers to a greater risk of damage when cutting off such a short-circuit current. It is thus required that the circuit breakers be inspected at regular intervals of time to exchange the contacts depending on the degree of damage.
In an enclosed-type circuit breaker in which the contacts are covered with partition walls or casing, it requires very troublesome and time-consuming work to check the degree of their damage. Also, since it is required to cut off the power supply during the work including removal of the partitions or casing, the working time must be as short as possible. Further, in order to minimize the time required for maintenance and inspection of the circuit breaker for saving maintenance labor, it is desirable to lengthen the time intervals between successive regular inspections on the one hand and to shorten the time required for each regular inspection on the other hand. In the case where the contacts are determined faulty as a result of the regular inspection, it is inevitable that the enclosed parts be dismantled in order to replace the contacts, while when the contacts are in good condition they need not be replaced. Therefore, if it is possible to detect the good condition of the contacts without visual inspection, it will eliminate the need of the labor-consuming work of dismantling and assembly of the enclosed parts, desirably resulting in a shorter time of power stoppage and an improved maintenance labor saving.